CN220292017U - Radio frequency front-end circuit of dual-frequency receiver - Google Patents
Radio frequency front-end circuit of dual-frequency receiver Download PDFInfo
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- CN220292017U CN220292017U CN202321881512.4U CN202321881512U CN220292017U CN 220292017 U CN220292017 U CN 220292017U CN 202321881512 U CN202321881512 U CN 202321881512U CN 220292017 U CN220292017 U CN 220292017U
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Abstract
The embodiment of the utility model discloses a radio frequency front-end circuit of a double-frequency receiver, which comprises a first radio frequency receiving channel, a second radio frequency receiving channel and a frequency synthesizer, wherein the first radio frequency receiving channel and the second radio frequency receiving channel are respectively formed by a low-noise amplifier, a mixer unit, a complex band-pass filter, an adjustable gain amplifier and an analog-to-digital converter which are sequentially connected, and the mixer units comprise a first mixer, a second mixer, a third mixer and a fourth mixer. The utility model only uses one frequency synthesizer to realize the double-frequency signal receiving; the area and the power consumption of the LNA can be small under the current technical condition, so that the circuit cost of the two LNAs is not increased; the utility model does not use an off-chip intermediate frequency filter to realize image rejection inside the chip; the utility model does not use a complex signal synthesis filter, and reduces the design cost and the circuit complexity; the automatic gain control of each channel of the present utility model is capable of independent operation.
Description
Technical Field
The utility model relates to the technical field of radio frequency, in particular to a radio frequency front-end circuit of a dual-frequency receiver.
Background
The conventional dual-band receiver rf front-end circuit comprises two independent rf channels, each comprising an independent low noise amplifier LNA, a MIXER, a filter LPF, a variable gain amplifier PGA, an analog-to-digital converter ADC, and a frequency synthesizer PLL. Thus, the circuit cost for receiving the dual-frequency signal is twice that of the single-frequency receiver, as shown in fig. 1.
Some modifications are as disclosed in CN201010620937.0, "a single chip dual frequency global satellite navigation receiver", as shown in fig. 2. Patent CN201010620937.0 contains two independent radio frequency channels, and patent CN201010620937.0 can be configured in two reception modes compared to fig. 1: the first is a low intermediate frequency/zero intermediate frequency receiving mode, because the signals of the receiving channel A and the receiving channel B are mirror images, when the receiving channel A is opened, the signal of the receiving channel B can be restrained, and single-frequency receiving is realized; the second is a superheterodyne receiving mode, the dual-frequency signal enters into 41 and 42 receiving channels respectively, at this time, the off-chip filter LC BPF 406/425 is turned on, and the two frequency synthesizers are a radio frequency synthesizer (1.1 GHz-1.6 GHz) and an intermediate frequency synthesizer (150 MHz-220 MHz) respectively, so that the interaction between the two frequency synthesizers can be reduced, but the off-chip intermediate frequency filter is used, which is unfavorable for chip integration, and the cost is increased.
Patent CN201010206235.8 proposes a "dual system dual frequency navigation receiver rf front end device", as shown in fig. 3. Similar to the patent CN201010620937.0, the second down-conversion technique is also adopted, and the first down-conversion is performed to obtain the high intermediate frequency signal 110MHz-220MHz, so that the image signal needs to be suppressed by the off-chip filter 4, which is also unfavorable for chip integration.
The method disclosed in the patent CN201510404289.8 is as shown in fig. 4, the characteristic that different frequency bands are mirror images is well utilized, the image rejection is realized by using only an internal circuit of a chip without using an off-chip intermediate frequency filter, and only one frequency synthesizer is needed, so that the frequency generated by the frequency synthesizer is skillfully designed, and the dual-frequency receiving is realized. However, this utility model has three problems: first, the module 40 is a filter with signal synthesis function, which has more difficulty in designing than a general filter, and requires more components with larger area, which increases design complexity and circuit cost; second, to receive the GNSS navigation satellite signals of 1150MHz-1510MHz, the module 10 is a broadband low noise amplifier, which receives more interference signals while receiving signals, reducing the signal-to-noise ratio of the circuit; third, the rf receiver generally designs an AGC circuit so that when the input energy changes, the AGC can adjust the overall gain of the rf receiver, and ensure that the ADC outputs more stable energy to process the baseband, but the first and second channels of CN201510404289.8 share a wideband low noise amplifier, and when an interference frequency exists in one channel, the AGC can adjust the gain of the first and second channels at the same time, so that the signal-to-noise ratio of the other receiving channel cannot be maximized.
The approaches disclosed in patent CN201010620937.0 and patent CN201010206235.8 require the use of off-chip intermediate frequency filters, which are disadvantageous for chip integration and have high cost.
The method disclosed in patent CN201510404289.8 has a great difficulty in designing a filter with a synthesizing function, and the wideband LNA captures more interference energy, so that the method of sharing the LNA is not beneficial to automatic gain control of the receiver.
Disclosure of Invention
The technical problem to be solved by the embodiment of the utility model is to provide a radio frequency front-end circuit of a dual-frequency receiver, so that the design cost and the circuit cost are reduced, and the automatic gain control of each channel can be independently operated.
In order to solve the technical problems, the embodiment of the utility model provides a radio frequency front-end circuit of a dual-frequency receiver, which comprises a first radio frequency receiving channel, a second radio frequency receiving channel and a frequency synthesizer, wherein the first radio frequency receiving channel and the second radio frequency receiving channel are respectively composed of a low-noise amplifier, a mixer unit, a complex band-pass filter, an adjustable gain amplifier and an analog-to-digital converter which are sequentially connected, the mixer units comprise a first mixer, a second mixer, a third mixer and a fourth mixer, the first mixer is connected with the second mixer in series, the third mixer is connected with the fourth mixer in series, the first mixer and the third mixer receive signals of the low-noise amplifier, and output signals of the second mixer and the fourth mixer are superposed on the complex band-pass filter.
Further, the frequency synthesizer outputs first local oscillator signals LO1_i and LO1_q and second local oscillator signals LO2_i and LO2_q, wherein LO1_i and LO1_q are identical in frequency but are 90 degrees out of phase; the LO2_I and LO2_Q frequencies are identical, but are 90 degrees out of phase; the first mixer and the third mixer of the first radio frequency receiving channel receive first local oscillator signals LO1_Q and LO1_I, and the second mixer and the fourth mixer of the first radio frequency receiving channel receive second local oscillator signals LO2_Q and LO2_I; the first mixer and the third mixer of the second radio frequency receiving channel receive the first local oscillation signals LO1_Q and LO1_I, and the second mixer and the fourth mixer of the second radio frequency receiving channel receive the second local oscillation signals LO2_I and LO2_Q.
Further, the angular frequency w of the first local oscillator signal 1 The method meets the following conditions:
w 1 =（w A +w B ）/2；
wherein w is A And w B Angular frequencies of signals entering the first radio frequency receiving channel and the second radio frequency receiving channel respectively;
angular frequency w of second local oscillation signal 2 The method meets the following conditions:
w 2 =w 1 /N；
n is 1 or more.
The beneficial effects of the utility model are as follows:
1. the utility model only uses one frequency synthesizer to realize the double-frequency signal receiving; the area and the power consumption of the LNA can be small under the current technical condition, so that the circuit cost of the two LNAs is not increased;
2. the utility model does not use an off-chip intermediate frequency filter to realize image rejection inside the chip;
3. the utility model does not use a complex signal synthesis filter, and reduces the design cost and the circuit complexity;
4. the automatic gain control of each channel of the present utility model is capable of independent operation.
Drawings
Fig. 1 is a schematic diagram of a conventional rf front-end circuit of a dual-band receiver.
Fig. 2 is a schematic structural diagram of patent CN 201010620937.0.
Fig. 3 is a schematic structural diagram of patent CN 201010206235.8.
Fig. 4 is a schematic structural diagram of patent CN 201510404289.8.
Fig. 5 is a schematic structural diagram of a radio frequency front-end circuit of a dual-band receiver according to an embodiment of the present utility model.
Description of the reference numerals
A low noise amplifier 10, a mixer unit 20, a complex band-pass filter 30, an adjustable gain amplifier 40, an analog-to-digital converter 50 of the first radio frequency receiving channel; the low noise amplifier 11 of the second radio frequency receiving channel, the mixer unit 21, the complex band-pass filter 31, the adjustable gain amplifier 41, the analog-to-digital converter 51.
Detailed Description
It should be noted that, without conflict, the embodiments and features of the embodiments in the present application may be combined with each other, and the present utility model will be further described in detail with reference to the drawings and the specific embodiments.
In the embodiment of the present utility model, if there is a directional indication (such as up, down, left, right, front, and rear … …) only for explaining the relative positional relationship, movement condition, etc. between the components in a specific posture (as shown in the drawings), if the specific posture is changed, the directional indication is correspondingly changed.
In addition, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implying an indication of the number of features being indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.
Referring to fig. 5, a dual-band receiver rf front-end circuit according to an embodiment of the present utility model includes a frequency synthesizer, a first rf receiving channel and a second rf receiving channel.
As shown in fig. 5, the first radio frequency receiving channel is composed of a low noise amplifier 10 (LNA), a MIXER unit 20 (MIXER), a complex band-pass filter 30 (CBPF), an adjustable gain amplifier 40 (PGA), and an analog-to-digital converter 50 (ADC) connected in sequence, and the second radio frequency receiving channel is composed of a low noise amplifier 11 (LNA), a MIXER unit 21 (MIXER), a complex band-pass filter 31 (CBPF), an adjustable gain amplifier 41 (PGA), and an analog-to-digital converter 51 (ADC) connected in sequence.
The mixer units comprise a first mixer, a second mixer, a third mixer and a fourth mixer, as shown in fig. 5, the first mixer and the second mixer of the first row are connected in series, and the third mixer and the fourth mixer of the second row are connected in series. The first mixer and the third mixer receive signals of the low-noise amplifier, and the second mixer and the fourth mixer output low-intermediate frequency/zero-intermediate frequency signals to be overlapped to the complex band-pass filter.
The utility model realizes the receiving of the required signal and the suppression of the image signal through the mixer unit with the synthesis function.
The frequency synthesizer outputs first local oscillator signals LO1_I and LO1_Q and second local oscillator signals LO2_I and LO2_Q. Wherein, the LO1_I and LO1_Q frequencies are consistent, but the phase difference is 90 degrees; the LO2_ I and LO2_ Q frequencies are identical but are 90 degrees out of phase.
The first mixer and the third mixer of the first radio frequency receiving channel receive first local oscillator signals LO1_Q and LO1_I, and the second mixer and the fourth mixer of the first radio frequency receiving channel receive second local oscillator signals LO2_Q and LO2_I; the first mixer and the third mixer of the second radio frequency receiving channel receive the first local oscillation signals LO1_Q and LO1_I, and the second mixer and the fourth mixer of the second radio frequency receiving channel receive the second local oscillation signals LO2_I and LO2_Q.
As one embodiment, the angular frequency w of the first local oscillator signal 1 The method meets the following conditions:
w 1 =（w A +w B ）/2；
wherein w is A And w B The signals entering the first RF receiving channel and the second RF receiving channel (hereinafter referred to as frequency-signal sum frequencyRate two signal) angular frequency;
angular frequency w of second local oscillation signal 2 The method meets the following conditions:
w 2 =w 1 /N；
n is 1 or more. That is, the first local oscillation frequency is N times the second local oscillation frequency, N is greater than or equal to 1, and N is not limited to an integer or a decimal.
The utility model adopts a frequency synthesizer, and realizes double-frequency receiving by selecting the frequencies of the first local oscillator and the second local oscillator.
The working principle of the radio frequency front-end circuit of the dual-frequency receiver in the embodiment of the utility model is as follows:
1. dual-frequency signal w with LO1 frequency as an image A And w B Simultaneously enter a first radio frequency receiving channel (channel one for short) and a second radio frequency receiving channel (channel two for short), and assume a frequency of a signal w A Lower than the frequency of the second signal w B Wherein w is A And w B Angular frequencies of the first and second frequency signals, respectively, assuming that the dual frequency input signal is denoted as a=cos (w A t)+cos(w B t)。
2. The LNA 10 of the first channel amplifies the first frequency signal, reduces the noise contribution of the later module at the first frequency, and the second frequency signal serving as an image signal is also amplified, but the amplification degree is not as high as the first frequency; the second LNA 11 amplifies the second frequency signal and reduces the noise contribution of the subsequent module at the second frequency, and the first frequency signal is amplified as an image signal, but the amplification degree is not as large as the second frequency signal.
3. The amplified dual-frequency signals in the first channel and the second channel enter a mixer unit with a synthesis function.
4. The mixer cell principle is as follows:
a) The first local oscillator signals Ls1_I and Ls1_Q may be respectively represented by cos (w 1 t) and sin (w 1 t) is represented, the second local oscillator signals LO2_I and LO2_Q may be represented by cos (w) 2 t) and sin (w 2 t) is represented by w 1 And w 2 Angular frequencies of the first local oscillator and the second local oscillator respectively; the frequency of the first local oscillator may be set approximately atThe frequency of the second local oscillator can be set at w in the middle of the frequency of the received dual-frequency signal 1 N, the frequency of the frequency-signal is approximately equal to w 1 -w 1 N, the frequency of the frequency two signal is approximately equal to w 1 +w 1 N (for example, assuming that the frequency one signal is 1.2GHZ and the frequency two signal is 1.6GHZ, then LO1 may be set around 1.4GHZ, then LO2 may be set around 1.6GHZ to satisfy LO1+LO2, so that LO1-LO2 is around 1.2 GHZ; different LO1 and LO2 values may be chosen depending on the design, but only if this condition is satisfied; w 1 And w 2 To represent the frequency, w 1 The device is arranged near the middle of the dual-frequency signal. ) The method comprises the steps of carrying out a first treatment on the surface of the
b) The signal obtained by performing secondary frequency conversion on the channel one-double frequency signal can be expressed as: cos (w) 1 t)*cos(w 2 t)+A*sin(w 1 t)*sin(w 2 t)=A*cos(w 1 t-w 2 t)=A*cos((w 1 -w 1 /N)t)= (cos(w A t)+cos(w B t))*cos((w 1 -w 1 /N)t)=(cos((w A -w 1 +w 1 /N)t)+cos((w A +w 1 -w 1 /N)t)+ cos((w B -w 1 +w 1 /N)t)+cos((w B +w 1 -w 1 /N)t))/2；
c) The signal obtained by the channel two-frequency signal after the secondary frequency conversion can be expressed as: cos (w) 1 t)*sin(w 2 t)+A*sin(w 1 t)*cos(w 2 t)=A*sin(w 1 t+w 2 t)=A*sin((w 1 +w 1 /N)t)= (cos(w A t)+cos(w B t))*cos((w 1 +w 1 /N)t)=(cos((w A -w 1 -w 1 /N)t)+cos((w A +w 1 +w 1 /N)t)+ cos((w B -w 1 -w 1 /N)t)+cos((w B +w 1 +w 1 /N)t))/2；
d) Since the input signal A includes a lower-frequency signal and a higher-frequency signal, the frequency of the lower-frequency signal is w A Just at frequency (w 1 -w 1 near/N), frequency two signal frequency w B Just at frequency (w 1 +w 1 After the second down-conversion and signal synthesis, the first channel signal falls to a low intermediate frequency near zero frequency, as in the first term of step b, while the second, third and fourth terms are at a higher intermediate frequency; the second signal of the second channel will fall to the low intermediate frequency near the zero frequency, as in the third item of step c, and the second and fourth items are all located at the higher intermediate frequency; thus, the simultaneous receiving of the double-frequency signals is realized by only one frequency synthesizer, and only one signal positioned at the low intermediate frequency is received in each channel; other frequency items are all located at a higher intermediate frequency and can be filtered out by a post-filter.
5. The down-converted signal passes through a complex band-pass filter, so that the unwanted high-frequency signal can be filtered, the needed low-frequency signal is reserved, and the sideband energy opposite to the signal frequency is filtered through the complex band-pass filter, so that the overall signal-to-noise ratio of the receiver is improved.
6. The two-channel variable gain amplifier and the analog-to-digital converter complete the functions of amplifying and analog-to-digital converting signals and send the signals to a digital baseband for further signal processing, so that the function of the whole radio frequency front-end circuit is realized.
The mixer unit works in a current mode, can simply realize the function of current addition, does not need a filter with a combining function, and simplifies the design complexity; the image suppression is realized inside the chip, an external LC band-pass filter is not needed, the chip integration level is improved, and the circuit cost is reduced; the narrow-band LNA reduces the received interference energy and improves the signal-to-noise ratio of the circuit; the two channels independently work, the system AGC can independently control the gain of each radio frequency channel, and the system structure is more reasonable.
Although embodiments of the present utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the spirit and scope of the utility model as defined by the appended claims and their equivalents.
Claims (3)
1. The radio frequency front-end circuit of the double-frequency receiver comprises a first radio frequency receiving channel and a second radio frequency receiving channel, and is characterized by further comprising a frequency synthesizer, wherein the first radio frequency receiving channel and the second radio frequency receiving channel are respectively composed of a low-noise amplifier, a mixer unit, a complex band-pass filter, an adjustable gain amplifier and an analog-to-digital converter which are sequentially connected, the mixer units comprise a first mixer, a second mixer, a third mixer and a fourth mixer, the first mixer and the second mixer are connected in series, the third mixer and the fourth mixer are connected in series, the first mixer and the third mixer receive signals of the low-noise amplifier, and output signals of the second mixer and the fourth mixer are superposed on the complex band-pass filter.
2. The dual-frequency receiver radio frequency front-end circuit of claim 1, wherein the frequency synthesizer outputs first local oscillator signals LO 1I and LO 1Q and second local oscillator signals LO 2I and LO 2Q, wherein LO 1I and LO 1Q are identical in frequency but out of phase by 90 degrees; the LO2_I and LO2_Q frequencies are identical, but are 90 degrees out of phase; the first mixer and the third mixer of the first radio frequency receiving channel receive first local oscillator signals LO1_Q and LO1_I, and the second mixer and the fourth mixer of the first radio frequency receiving channel receive second local oscillator signals LO2_Q and LO2_I; the first mixer and the third mixer of the second radio frequency receiving channel receive the first local oscillation signals LO1_Q and LO1_I, and the second mixer and the fourth mixer of the second radio frequency receiving channel receive the second local oscillation signals LO2_I and LO2_Q.
3. The dual-band receiver radio frequency front-end circuit of claim 1, wherein an angular frequency w of the first local oscillator signal 1 The method meets the following conditions:
w 1 =（w A +w B ）/2；
wherein w is A And w B Angular frequencies of signals entering the first radio frequency receiving channel and the second radio frequency receiving channel respectively;
angular frequency w of second local oscillation signal 2 The method meets the following conditions:
w 2 =w 1 /N；
n is 1 or more.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202321881512.4U CN220292017U (en) | 2023-07-18 | 2023-07-18 | Radio frequency front-end circuit of dual-frequency receiver |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202321881512.4U CN220292017U (en) | 2023-07-18 | 2023-07-18 | Radio frequency front-end circuit of dual-frequency receiver |
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